This invention relates generally to imaging systems and methods. More particular, this invention relates to methods of detecting and correcting transient pixel defects in digital images produced by an imaging system.
Various imaging systems including X-ray radiography, single photon emission computed tomography (SPECT), positron emission tomography (PET), magnetic resonance imaging (MRI), and ultrasound imaging etc. are known and used in acquisition of images. In each imaging system, some kind of detector is used to detect electromagnetic radiation passed through a body of interest. For instance, an X-ray image acquisition system may employ a solid state detector having a detector array including a large number of detector elements or pixels. The detector elements produce image data signals which can be collected, stored, processed, and displayed as digital images. The images acquired may provide detailed information on the structures inside the body of interest, which is useful e.g. in medical diagnosis, security inspection, and other applications.
It is known that a detector array may include defective pixels formed in the course of manufacturing or use of the detector. Defective pixels either do not respond electrically under operation conditions or respond significantly differently from surrounding pixels. Accordingly, a detector may lose information or produce incorrect information in images at locations which contain defective pixels. Defective pixels in a detector are typically identified in a defect map created when the detector is tested or calibrated. In use image data acquired by the detector is compensated or corrected using the defect map and some kind of algorithms known in the art.
There are instances where a pixel of a detector behaves properly almost all of the time but on very rare occasions produces a value that deviates from its proper value. Such defect is referred to as transient defect. Transient defect may occur at any pixel in a detector although it rarely occurs. A pixel of a detector producing transient defect is not necessarily a defective pixel or a property of that detector element. While the causes of forming transient defects are unknown, detection and correction of transient defects is important to ensure accurate production of images useful for medical diagnosis or other applications.